1. Field of the Invention
The present invention relates generally to gear shifting devices for bicycles and other ridden vehicles having cable-actuated shifters. More particularly, the invention relates to an incremental gear shifting device employable to change gears on bicycles having conventional Bowden cables communicating with internally geared multi-speed rear hubs and derailleurs. The device includes an index plate having multiple sets of indexing apertures and limiting slots. Registered engagement of the index plate with a cavity allows the user to choose the set of indexing apertures which matches the shift points of a particular internally geared hub or derailleur in order to translate a precise amount of cable in preset increments as a shifting lever is pulled or rotated.
2. Prior Art
Bicycles have been in existence for centuries and are considered a most favorable means of transportation throughout the world. The majority of bicycles conventionally known in the art employ a chain to transmit power from the human operated crank to the rear wheel which is referred to as the drive train. More recently in history, gearing of the bicycle drive train has been employed which essentially determines the torque required to rotate the pedals and the relation between the the rate at which the rider pedals the crank, and the rate at which the rear wheel turns. This relationship between force required to rotate the pedals and the rate the pedals are rotated to rotate the drive wheel is determined by the size and number of teeth of the gear employed on the crank, and the size and number of teeth of the gear employed on the rear wheel, wherein the relationship is referred to as the ‘gear ratio’.
The majority of modern bicycles employ multiple gears on the pedal axle as well as the drive wheel axle and thus are capable of multiple gear ratios between the two and changing the mechanical advantage of the system to the riding conditions and user strength. Conventionally, a gear shifting device is provided which allows users to select the appropriate gear ratio as needed for the application of a comfortable pedal force to yield improved riding efficiency depending on their certain riding style, the terrain, or simply the rider's current preference.
As a simple example, it is conventional for riders to employ a high gear ratio (i.e. large gear at the crank, and smaller gear at the rear wheel) when cycling downhill since the torque required to turn the pedal is lessened by gravity acting on the bike during a downhill run. A medium gear may generally be employed when cycling on a flat road where there is little uphill resistance which would increase pedal torque requirements.
Riding uphill, where gravity acts to increase the torque required on the pedals, a low gear ratio (i.e. relatively smaller gear at the crank, and a larger gear at the rear wheel) is employed.
Although many gear shifting systems have been taught throughout history, there are mainly two especially preferred shifting systems employed widely today, one employing derailleur gears, and the other, internal hub gears.
Derailleur gears comprise multiple sprockets of different sizes employed on one or both of the crank and rear wheel, and a shifting mechanism and biased take-up of the chain to allow the chain to adapt from one sprocket to another to achieve the desired gear ratio. Internal hub gears consist generally of planetary or epicyclic gears which are sealed and lubricated within a shell of the hub gear. Briefly, the number of available gear ratios is generally referred to as the ‘speed’ of the bicycle, that is, a gear system capably of 3 gear ratios is referred to as a ‘3-speed’, a gear system having 5 different possible gear ratios is a ‘5-speed’, and so forth.
Although there exists some advantages of employing one system over the other, the choice of which system to employ is more than often merely the personal preference of the designer. Further, since the inception of the Bowden cable in the late 1890's, both shifting devices are capable of shifting operation via the translation of the cable by a shift lever employed by the user for gear selection. In general, the shift lever and operatively engaged cable are employed to translate a precise amount of cable, in preset increments, as a shifting lever is pulled or rotated a distance, in order to move the chain from one sprocket to another in derailleur type gears, or to change the gear ratios within the planetary gears for internal hub type gear systems. As a brief note, the length the cable translates between the present incremental points corresponding to different gear ratios is generally referred to as the ‘cable-pull’.
Currently, due to the competitive market of bicycles and brand recognition, many manufacturers of internally geared bicycle hubs and derailleur gears additionally manufacture proprietary shifters. As a result of such proprietary components, many shifters are manufactured to only work with one type or model of hub or derailleur.
For example, a shifter mechanism for a certain model derailleur or hub gear may be configured with a specific cable throw and limiting index, which limit the cable-pull between the particular increments. The shift lever can be pulled or rotated about in a manner determined by the amount the cable needs to translate in either direction, to shift between gears of that specific gear system. Manufacturers may vary the increments to fit only their systems.
In addition, when changing parts, upgrading components, or performing maintenance on a bicycle, it is common for users to keep the same bicycle frame, but interchange the gearing systems as needed to change the bike from a 3-speed to a 5-speed, a 5-speed to a 7-speed, and so forth. Thus, users wishing to perform this task are frequently required to change both the gear system as well as the shifting mechanism, since the new gear system is only adapted to a proprietary shifter.
As could be imagined, this requirement, to change both shifter and shift system, can be quite costly especially in the event the user is moving to a gear system with a substantially increased number of potential gear combinations, typically having more components and therefor more costs. Further, in the event of repair or replacement of damaged parts, the user is required to employ only certain and sometimes proprietary parts and components which match their current manufacturer proprietary gear and shifter set, which may be difficult to acquire for out-dated or specialty manufacturers.
Currently, there exists no gear shifting device which is capable of adaptation cable translation for shifting to various gear system types, varying numbers of gear ratio combinations, brands, and manufacturers. This is due to the inconsistences with length and increments of cable pull required to shift between gears between different manufactured systems.
As a result, there is a continuing unmet need for a incremental gear shifting device which is configurable for operation with a plurality of different gearing systems by differing manufacturers, and varying gear ratios, by employing means for selecting from one of a plurality of available cable throw configurations. Such a device should provide this ability to change shifting configurations to the task at hand through the provision of an adjustable and replaceable index plate adapted to one or a plurality of manufactured systems.
Such a device should be adaptable to operate in concert with a plurality of known gear systems thereby providing a shifting device which is universally adaptable and employable and easily repaired or altered. Such a device, through the employment of an index plate having multiple sets of indexing apertures, and limiting slots, should be easily configurable to provide the user with a means for choosing the set of indexing apertures which is operable with the shift points of a particular internally geared hub or derailleur in order to translate a precise amount of cable, in preset increments, to afford precise shifting as a shifting lever is pulled or rotated.
The forgoing examples of related art and limitation related therewith are intended to be illustrative and not exclusive, and they do not imply any limitations on the invention described and claimed herein. Various limitations of the related art will become apparent to those skilled in the art upon a reading and understanding of the specification below and the accompanying drawings.